Oxidation catalyst for waste heat recovery performance improvement

ABSTRACT

An exhaust system for an engine include a first exhaust system portion that receives exhaust from one or more combustion chambers of the engine. The exhaust system also includes an oxidation catalyst having an inlet and an outlet. The inlet of the oxidation catalyst is in fluid communication with the first exhaust system portion and receives exhaust from the one or more combustion chambers of the engine. The exhaust system also includes a second exhaust system portion that receives exhaust gases downstream from the outlet of the oxidation catalyst. A waste heat recovery system is in thermal communication with the second exhaust system portion that receives exhaust gases from the outlet of the oxidation catalyst. In some instances, the exhaust system may omit other aftertreatment components.

FIELD OF THE INVENTION

The present application relates generally to the field of waste heat recovery systems for use with internal combustion engines.

BACKGROUND

For internal combustion engines, such as ignition spark engines, the exhaust system may include a waste heat recovery system that can capture a portion of heat energy that normally would be wasted (i.e., “waste heat”) and convert a portion of the captured heat energy into energy that can perform useful work. For example, heat from an internal combustion engine system, such as exhaust gas heat energy or other engine waste heat sources (e.g., engine oil, charge gas, engine block cooling jackets) can be captured and converted to useful energy (e.g., electrical and/or mechanical energy). In this way, a portion of the waste heat energy can be recovered to increase the efficiency of a system including one or more waste heat sources.

SUMMARY

One implementation relates to an apparatus that includes an engine and an exhaust system in fluid communication with one or more combustion chambers of the engine. The exhaust system includes an oxidation catalyst having an inlet and an outlet. The inlet of the oxidation catalyst is in fluid communication with a first portion of the exhaust system and receives exhaust from the one or more combustion chambers of the engine. A Rankine waste heat recovery system is in thermal communication with a second portion of the exhaust system. The second portion of the exhaust system is coupled to the outlet of the oxidation catalyst and receives exhaust gases downstream from the oxidation catalyst.

Another implementation relates to an exhaust system for an engine that includes a first exhaust system portion that receives exhaust from one or more combustion chambers of the engine. The exhaust system also includes an oxidation catalyst having an inlet and an outlet. The inlet of the oxidation catalyst is in fluid communication with the first exhaust system portion and receives exhaust from the one or more combustion chambers of the engine. The exhaust system also includes a second exhaust system portion that receives exhaust gases downstream from the outlet of the oxidation catalyst. The exhaust system also includes a Rankine waste heat recovery system in thermal communication with the second portion of the exhaust system.

Yet another implementation relates to a method of manufacturing an exhaust system. The method includes providing an exhaust system, an oxidation catalyst, and a Rankine waste heat recovery system. The method includes coupling a portion of the Rankine waste heat recovery system to a second portion of the exhaust system such that a portion of the Rankine waste heat recovery system is in thermal communication with the second portion of the exhaust system. The method also includes coupling an inlet of the oxidation catalyst to a first portion of the exhaust system to receive exhaust gases from an engine and an outlet of the oxidation catalyst to the second portion of the exhaust system.

BRIEF DESCRIPTION OF THE DRAWINGS

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the disclosure will become apparent from the description, the drawings, and the claims, in which:

FIG. 1 is a block schematic diagram of an exhaust system from an engine having a waste heat recovery system and an oxidation catalyst positioned upstream of the waste heat recovery system; and

FIG. 2 is a block diagram of an implementation of a method of manufacturing an exhaust system with an oxidation catalyst upstream of a waste heat recovery system.

It will be recognized that some or all of the figures are schematic representations for purposes of illustration. The figures are provided for the purpose of illustrating one or more implementations with the explicit understanding that they will not be used to limit the scope or the meaning of the claims.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various concepts related to, and implementations of, methods, apparatuses, and systems for providing an oxidation catalyst upstream of a waste heat recovery system. The various concepts introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the described concepts are not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.

I. Overview

For spark-ignited engines, such as natural gas engines, a larger concentration of unburned hydrocarbons and/or carbon monoxide may be present in the exhaust gas. For instance, spark-ignited engines may have a combustion efficiency of approximately 98%. Thus, approximately 2% of the fuel energy is not utilized and leaves the engine as unburned hydrocarbons and/or carbon monoxide. In some implementations, a waste heat recovery system may be included as part of the exhaust system to capture the heat of the exhaust gases and convert the heat to useful energy (e.g., electrical and/or mechanical energy). To maximize the usage of the fuel, an oxidation catalyst may be positioned upstream of the waste heat recovery system to oxidize the unburned hydrocarbons and/or carbon monoxide, thereby producing additional heat for the exhaust gases. Such additional heat may be captured by the waste heat recovery system and converted into electrical or mechanical energy. In some implementations, the oxidation catalyst may be configured or optimized for natural gas and/or carbon monoxide. In some implementations the oxidation catalyst and waste heat recovery systems may be utilized with engines that do not have or require aftertreatment systems. The system may also be particularly useful in arrangements where there is no aftertreatment system, and particularly no after treatment system containing a particulate filter or the like.

II. Implementation of Exhaust System Having Oxidation Catalyst and Waste Heat Recovery System

FIG. 1 depicts an exhaust system 100 for an engine 190 having an oxidation catalyst 110 and a waste heat recovery system 120. The engine 190 may be a spark-ignited engine, such as a natural gas spark-ignited engine in some implementations. In some instances, the engine 190 may be a high horse power natural gas spark-ignited engine. Such an engine 190 may meet emissions standards using lean burn technology and may omit aftertreatment systems. In some implementations, the engine 190 may be incorporated as part of a power generation unit, such as a generator or power plant. In other implementations, the engine 190 may be incorporated as an engine for a vehicle.

The oxidation catalyst 110 is in fluid communication with the engine 190 to oxidize hydrocarbons and/or carbon monoxide in the exhaust gas from the engine 190. In the present example, the oxidation catalyst 110 is in fluid communication with the engine 190 via two exhaust manifolds 102 from the engine 190 that combine in a single inlet 104 for the oxidation catalyst 110. In other implementations, each exhaust manifold 102 may be in fluid communication with separate inlets 104 to the oxidation catalyst 110. The oxidation catalyst 110 includes a single outlet 106 leading to the rest of the exhaust system 100 and is upstream of the waste heat recovery system 120. Each exhaust manifold 102 may aggregate exhaust gas from several combustion chambers of the engine 190. For instance, each exhaust manifold 102 may be coupled to the engine 190 and corresponds to a set of combustion chambers on a corresponding side of an internal combustion engine 190 (e.g., for a V-shaped engine, a left manifold 102 may receive and aggregate exhaust gases from the set of combustion chambers on the left side of the V shape). In some implementations, one or more turbochargers may be included between each exhaust manifold 102 and the inlet 104.

The oxidation catalyst 110 receives the exhaust gases from the inlet 104 and oxidizes the unburned hydrocarbons and/or carbon monoxide into carbon dioxide and water. The oxidation process also produces additional heat that heats the exhaust gases flowing through the oxidation catalyst 110. In some implementations, the oxidation catalyst 110 can include catalysts such as ceramic or metal substrates coated with a washcoat and/or precious metals. The precious metals may include one or more of platinum, palladium, and/or rhodium. The precious metal loading can vary based on the chemical to be oxidized, the inlet temperature, and/or the desired conversion efficiency. In some implementations, the oxidation catalyst 110 may be configured or optimized for natural gas and/or carbon monoxide. In some implementations, the oxidation catalyst 110 may be upstream of one or more turbochargers. Positioning the oxidation catalyst 110 upstream of one or more turbines of one or more turbochargers may provide additional energy to the turbines, but less to a waste heat recovery system 120. Such a positioning of the oxidation catalyst 110 upstream of one or more turbochargers may assist with the transient response or pumping losses. In other implementations, the oxidation catalyst 110 may be downstream of the one or more turbochargers to maximize the waste heat recovery system 120 extraction potential when no extra energy is desired for the one or more turbines or the one or more turbochargers.

The additionally heated exhaust gas from the oxidation catalyst 110 leaves the oxidation catalyst 110 via an outlet 106 that is downstream and in fluid communication with the oxidation catalyst 110. The outlet 106 is further in fluid communication with a second portion of the exhaust system 100 that is in thermal communication with a portion of the waste heat recovery system 120. In some implementations, the portion of the waste heat recovery system 120 that is in thermal communication with the second portion of the exhaust system 100 may be disposed within the second portion of the exhaust system 100, disposed about the second portion of the exhaust system 100, and/or extend through the second portion of the exhaust system 100. The second portion of the exhaust system 100 receives the additionally heated exhaust gas from the oxidation catalyst 110 and thermally transfers the heat from the additionally heated exhaust gas to the portion of the waste heat recovery system 120. The waste heat recovery system 120 captures and converts the heat of the exhaust gas into useful energy (e.g., electrical and/or mechanical energy). In some implementations, the waste heat recovery system 120 may include a recuperator, a thermal wheel, a heat pump, and/or combinations thereof.

In some implementations, the waste heat recovery system 120 may include an organic Rankine cycle system. For instance, the waste heat recovery system 120 may include an organic Rankine cycle system that transfers thermal energy of the exhaust gases to a working fluid of the organic Rankine cycle system, although other types Rankine cycle working fluids can be used. In some implementations, the portion of the waste heat recovery system 120 in thermal communication with the second portion of the exhaust system 100 may include a boiler or heat exchanger in heat exchange communication with the exhaust gases within the exhaust system 100 downstream of the oxidation catalyst 110. For instance, the boiler or heat exchanger may include a heat exchange passage extending within, about, and/or through the second portion of the exhaust system 100. Thus, exhaust gases flowing through the exhaust system 100 downstream of the oxidation catalyst 110 transfer heat to the working fluid within the heat exchange passage. In the boiler or heat exchanger, the working fluid boils off and produces a high pressure vapor that exits the boiler or heat exchanger and flows to an inlet of an energy conversion device, such as a high pressure expander (e.g., a turbine).

The energy conversion device of the waste heat recovery system 120 is capable of producing additional work or transferring energy to another device or system. For instance, the energy conversion device can be a turbine that rotates as a result of the expanding working fluid vapor to provide additional work, which can be fed into the engine's driveline to supplement the engine's power either mechanically or electrically (e.g., by turning a generator), used to power electrical devices, and/or stored in a battery. Alternatively, the energy conversion device can be used to transfer energy from the waste heat recovery system 120 to another system.

The working fluid of the waste heat recovery system 120 can exit via an outlet of the energy conversion device (e.g., expanded gases of a turbine) and flow to a condenser, where it is cooled and condensed. The condenser can cool the working fluid directly with an air-cooled heat exchanger and/or with another liquid cooler. The condensed and cooled working fluid exits the outlet of the condenser and can be pressurized via a pump prior to being provided to the boiler or heat exchanger. The rankine cycle can also be done via a piston pump. In another implementation, a thermoelectric generator may be utilized as part of the waste heat recovery system 120 to generate electrical energy from the additionally heated exhaust gas from the oxidation catalyst 110. In still other implementations, the waste heat recovery system 120 may incorporate turbo-compounding to have a turbine downstream of the oxidation catalyst 110.

In some implementations, the waste heat recovery system 120 may be constructed in accordance with the teachings of U.S. Pat. No. 8,800,285, entitled “Rankine Cycle Waste Heat Recovery System,” issued Aug. 12, 2014, the disclosure of which is incorporated by reference herein in its entirety.

The exhaust gases leaving the second portion of the exhaust system 100 downstream of the waste heat recovery system 120 can exit to the remainder of the exhaust system 100 and/or be expelled to atmosphere. In some implementations, the exhaust system 100 may include one or more components downstream of the waste heat recovery system 120 for further treatment of the exhaust gases.

FIG. 2 depicts an implementation of a method 200 of manufacturing an exhaust system, such as exhaust system 100 with an oxidation catalyst 110 upstream of a waste heat recovery system 120. The method 200 includes providing an oxidation catalyst and a waste heat recovery system (block 210). The oxidation catalyst may be configured and/or optimized for natural gas and/or carbon monoxide. The waste heat recovery system may be an organic Rankine cycle waste heat recovery system or a non-organic Rankine cycle waste heat recovery system. The waste heat recovery system may include a boiler or heat exchanger.

The method 200 includes coupling a portion of the waste heat recovery system to be in thermal communication with a portion of the exhaust system (block 220). In some implementations, the portion of the waste heat recovery system may be a portion of a boiler or a heat exchanger of the waste heat recovery system that may be coupled to be in thermal communication with the portion of the exhaust system. For instance, a portion of the boiler or heat exchanger may be coupled to and/or positioned within a pipe of the exhaust system, a portion of the boiler or heat exchanger may be coupled to and/or positioned through a pipe of the exhaust system, and/or a portion of the boiler or heat exchanger may be coupled to and/or positioned about a pipe of the exhaust system. The boiler or heat exchanger of the waste heat recovery system may be in thermal communication with the exhaust system such that the waste heat recovery system receives heat from the exhaust system without being in fluid communication with the exhaust gases of the exhaust system.

The method 200 also includes coupling the oxidation catalyst to the exhaust system upstream of the waste heat recovery system (block 230). An outlet of the oxidation catalyst may be coupled to the portion of the exhaust system that is in thermal communication with the portion of the waste heat recovery system. For instance, the outlet of the oxidation catalyst may be coupled to the portion of the exhaust system that is in thermal communication with a portion of the boiler or heat exchanger of the waste heat recovery system. An inlet to the oxidation catalyst may be coupled to another portion of the exhaust system for receiving exhaust gases from an engine in fluid communication with the exhaust system.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular implementations. Certain features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

The terms “coupled,” “connected,” and the like as used herein mean the joining of two components directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two components or the two components and any additional intermediate components being integrally formed as a single unitary body with one another or with the two components or the two components and any additional intermediate components being attached to one another.

The terms “fluidly coupled,” “in fluid communication,” and the like as used herein mean the two components or objects have a pathway formed between the two components or objects in which a fluid, such as water, air, gaseous reductant, gaseous ammonia, etc., may flow, either with or without intervening components or objects. Examples of fluid couplings or configurations for enabling fluid communication may include piping, channels, or any other suitable components for enabling the flow of a fluid from one component or object to another.

It is important to note that the construction and arrangement of the system shown in the various exemplary implementations is illustrative only and not restrictive in character. All changes and modifications that come within the spirit and/or scope of the described implementations are desired to be protected. It should be understood that some features may not be necessary and implementations lacking the various features may be contemplated as within the scope of the application, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used, the item can include a portion and/or the entire item unless specifically stated to the contrary. 

What is claimed is:
 1. An apparatus, comprising: an engine; and an exhaust system in fluid communication with one or more combustion chambers of the engine, the exhaust system including: an oxidation catalyst having an inlet and an outlet, the inlet of the oxidation catalyst in fluid communication with a first portion of the exhaust system and receiving exhaust from the one or more combustion chambers of the engine, and a Rankine waste heat recovery system in thermal communication with a second portion of the exhaust system, the second portion of the exhaust system coupled to the outlet of the oxidation catalyst and receiving exhaust gases downstream from the oxidation catalyst.
 2. The apparatus of claim 1, wherein the Rankine waste heat recovery system is an organic Rankine cycle waste heat recovery system.
 3. The apparatus of claim 1, wherein the Rankine waste heat recovery system comprises a heat exchanger.
 4. The apparatus of claim 1, wherein the Rankine waste heat recovery system comprises a boiler.
 5. The apparatus of claim 1, wherein a portion of the Rankine waste heat recovery system is disposed within the second portion of the exhaust system.
 6. The apparatus of claim 1, wherein a portion of the Rankine waste heat recovery system is disposed about the second portion of the exhaust system.
 7. The apparatus of claim 1, wherein a portion of the Rankine waste heat recovery system extends through the second portion of the exhaust system.
 8. The apparatus of claim 1, wherein the exhaust system does not include a particulate filter.
 9. An exhaust system for an engine, consisting essentially of: a first exhaust system portion receiving exhaust from one or more combustion chambers of the engine; an oxidation catalyst having an inlet and an outlet, the inlet of the oxidation catalyst in fluid communication with the first exhaust system portion and receiving exhaust from the one or more combustion chambers of the engine; a second exhaust system portion receiving exhaust gases downstream from the outlet of the oxidation catalyst; and a Rankine waste heat recovery system in thermal communication with the second exhaust system portion.
 10. The exhaust system of claim 9, wherein the Rankine waste heat recovery system is an organic Rankine cycle waste heat recovery system.
 11. The exhaust system of claim 9, wherein the Rankine waste heat recovery system comprises a heat exchanger or a boiler.
 12. The exhaust system of claim 9, wherein a portion of the heat exchanger or boiler of the Rankine waste heat recovery system extends through the second exhaust system portion.
 13. The exhaust system of claim 9, wherein a portion of the heat exchanger or boiler of the Rankine waste heat recovery system is disposed about the second exhaust system portion.
 14. The exhaust system of claim 9, wherein the exhaust system does not include a particulate filter.
 15. A method of manufacturing an exhaust system comprising: providing an exhaust system, an oxidation catalyst, and a Rankine waste heat recovery system; coupling a portion of the Rankine waste heat recovery system to a second portion of the exhaust system such that the portion of the Rankine waste heat recovery system is in thermal communication with the second portion of the exhaust system; coupling an inlet of the oxidation catalyst to a first portion of the exhaust system to receive exhaust gases from an engine; and coupling an outlet of the oxidation catalyst to the second portion of the exhaust system.
 16. The method of claim 15, wherein the Rankine cycle waste heat recovery system is an organic Rankine cycle waste heat recovery system.
 17. The method of claim 15, wherein the portion of the Rankine waste heat recovery system is a portion of a heat exchanger or a boiler of the Rankine waste heat recovery system.
 18. The method of claim 17, wherein the coupling of the portion of a heat exchanger or a boiler of the Rankine waste heat recovery system comprises coupling the portion of the heat exchanger or boiler about the second portion of the exhaust system.
 19. The method of claim 17, wherein the coupling of the portion of a heat exchanger or a boiler of the Rankine waste heat recovery system comprises inserting the portion of the heat exchanger or boiler through the second portion of the exhaust system. 